Purpose: :
To assess the prevalence of refractive error in a preschoolpopulation in Australia and determine whether iris colour andits relationship to cycloplegia affect its measurement.

Methods: :
The Sydney Paediatric Eye Disease Study randomly selected apostcode from each of the Australian Bureau of Statistics inner,middle and outer geographical regions of Sydney. Householdsin the postcode were enumerated to determine eligible childrenaged 6 months to 6 years, who were then invited to participatein the study. Participating families provided written, informedconsent for their child/children to participate. Comprehensiveeye examinations were performed on each child, including cycloplegicrefraction, following 2 drops of cyclopentolate 1.0%, 5 minsapart (0.5% for children aged ≤12 months), using auto-refraction(Canon RK-F1 or Retinomax) or by retinoscopy. They were classifiedby spherical equivalent (SE) of the right eye. Iris colour wasgraded by reference photographs. Data from only the outer suburbansite is presented.

Results: :
Of the 1098 children who participated at this site (76% responserate), mild hyperopia (≥+0.5 to +2.0D) was the most prevalentrefractive state (70.1%) and myopia (≤-0.5D) was found in only2.4% of the population. Mean SE and myopia prevalence for childrenaged 6 to <12 months was +1.54D (SD 1.17), 2.0%; 12 to <24months +0.99 (SD 1.18), 4.3%; 24 to <36 months +1.17D (SD1.07), 1.7%; age 36 months or older +1.35D (SD 1.22), 1.8%.Mean SE in the 6 to <12 month group was not significantlydifferent from that in the oldest age group (p=0.5349). Thedistribution of refractive error in children with European Caucasianethnicity was more hyperopic than that in children with EastAsian (p<0.0001) or South Asian origin (p=0.2724). In EuropeanCaucasian children, iris colour ranging from blue to dark brownwas associated with a trend towards less hyperopic refractionbut only for ages >30 to 48 months.

Conclusions: :
Myopia was very uncommon at all ages in this population of Australianpreschool children, in contrast to recent US reports using similarprotocols. The prevalence of myopia in the 6 to <12 monthage group was not higher than other age groups and iris colourdid not appear to influence refraction measures. Children ofAsian ethnicity were however, significantly less hyperopic thantheir European Caucasian counterparts.